Yard and Garden – 05-19-2012 - Ted Griess / Extension Horticulture Assistant

Question: When is a geranium not a geranium? Answer: When the plant belongs to the genus Pelargonium. Sounds confusing, wouldn’t you agree?

Geranium is actually a genus name for a group of flowers involving over 400 species. Many are wildflowers. Some are annuals, some are biennials and others are perennials. Interestingly, their common name is cranesbills, not geranium.

What we so frequently refer to as a geranium is actually not a member of the genus Geranium; rather, it belongs to an entirely different genus, Pelargonium. Somehow, somewhere this group of plants acquired the common name we know as geranium. Today’s topic addresses this group.

Well over 200 Pelargoniums exist, and many are hybrids. These geraniums are among the most popular flowering plants. These groups of plants are treated as annuals since they will not survive Nebraska’s winters. They are most frequently grown as outdoor bedding plants, but they also make excellent houseplants if grown indoors in a sunny location.

Few plants offer such variation in flower color, growth habit, leaf pattern, and scent. Geranium flowers come in red, white, pink, salmon, fuchsia, lavender, and in bi-colors. There are double flower types and single types. Growth habits range from upright to trailing vines. The leaves range from nearly circular to deeply lobed. Leaf colors include multiple shades of green, variegated green and white and patterned combinations of reds, yellows, and oranges. When handling the plant, a distinctive odor is given off, a common characteristic of geraniums.

Often called the garden geranium and frequently referred to as a zonal geranium is the popular Pelargonium hortorum. This species often has fancy leaves marked by distinct bands of color. They serve well as annual bedding plants and are used widely in hanging baskets, window boxes or other planters.

As mentioned earlier, although most geranium flowers have a somewhat unpleasant odor, some emit pleasant scents. One popular scented geranium is Pelargonium citrosum, commonly called the mosquito geranium. This plant releases the odor of citronella. To most people, the smell of citronella is pleasant, but to mosquitoes, it is repulsive. I recall reading that one mosquito geranium will supposedly repel mosquitoes up to ten square feet. Other scented leaf geraniums include Pelargonium graveolens which is rose-scented, P. crispum which is lemon- scented, and P.x fragrans which is nutmeg-scented. There is even a vining geranium called Pelargonium peltatum. Its leaves are smooth, leathery and ivy-shaped. This vining species is often used in window boxes and baskets where it may grow to more than three feet in length.

Geraniums should not be planted outdoors until all danger of frost is past and the soil is warmed. They grow best where they receive a minimum of seven hours of sunlight daily. Flowering is reduced if grown in shade. Geraniums respond well to good fertility. Throughout the growing season, geraniums benefit from fertilization every four to six weeks. It is always best to use a slow release form of nitrogen. Water geraniums sufficiently to prevent wilting in the landscape ― at least once per week if rainfall is not adequate. When grown in pots, baskets or window boxes, daily watering may be needed. If possible, avoid wetting the foliage to prevent disease problems. If overhead watering is the only method available, water early enough in the day to allow the leaves and flowers to dry before nightfall.

Although not a member of the genus Geranium, the flowers we commonly call geraniums (actually members of the genus Pelargonium) certainly make excellent additions to any landscape, and when grown in containers, often create attractive focal points.

This year, rather than using peonies for Memorial Day (ours are completely done blooming), Rita and I have decided to use potted geraniums to decorate the graves. When the weekend is over, we will return them to our yard and enjoy them for the balance of the summer. I may even carry a few indoors in the fall, since geraniums make wonderful houseplants.